The present invention is based on a cordless screwdriver.
Cordless screwdrivers are already available in the power class between 2.4 V and 3.6 V, as known for instance from European Patent Disclosure 1 066 930. They usually have a plurality of NiCd cells as energy storing means; an ON/OFF button with a short toggle switch and without continuously variable speed governing, and a switch for switchover from counterclockwise to clockwise operation; a gear, in particular a planetary gear, that steps down the motor rpm; and a motor with a standard diameter of 27.5 mm. There are both rodlike and pistol-shaped versions as well as versions with an adjustable-angle handle. For charging, these devices are connected to the charger either via a plug—in a way similar to a cell phone or electric shaver—or via a mount with contacts, into which contacts the rechargeable battery can be placed for charging. The mounts can be secured to a wall, for instance, to make handling while charging easier.
For charging, the charging mode for the charger and for the electrical connection must be brought about, but this does not automatically happen after every use. As a result, the device is often not ready for use precisely when it is needed, and the well-known memory effect is a further disadvantage NiCd cells discharge after a certain length of time without outputting power, and even unused cordless screwdrivers become partly discharged after a short time. If they are charged when they are partly discharged, then because of the memory effect, after the charging operation, only the difference of the newly charged amount—and hence reduced power—is available.
A further disadvantage of the known cordless screwdrivers is their voluminous size because of large structural components, such as the gear, switch system, and the rechargeable battery in the form of NiCd cells, whose ⅘ sub-C size when located in the pistol grip is an impairment to ergonomics and utility, since narrow, angled places where screwing is to be done cannot be reached.
In known cordless screwdrivers with electrical secondary functions, such as a built-in work light, these functions have until now been switched on and off either separately with their own switch or actuating element or synchronously with the switch for the primary function, that is, the motor switch. If the secondary function can be switched separately, then there is the advantage that the light can be switched on as needed, for instance, and does not consume current constantly during operation of the power tool. A disadvantage is that for that purpose, a separate actuating element must first be operated. If by mistake this element is not switched off, the battery discharges unintentionally. This risk does not exist when the secondary function is switched synchronously with the primary function. In that case, however, the secondary function cannot be activated independently of the primary function, as is advantageous for instance with a work light of a screwdriver.